Further Improvements to ASME Section XI Code Case N-806 for Evaluation of Metal Loss in Class 2 and 3 Metallic Piping Buried in a Back-Filled Trench

Author(s):  
Robert O. McGill ◽  
Mark A. Moenssens ◽  
George A. Antaki ◽  
Douglas A. Scarth

ASME Section XI Code Case N-806, for evaluation of metal loss in Class 2 and 3 metallic piping buried in a back-filled trench, was first published in 2012. This Code Case has been prepared by the ASME Section XI Task Group on Evaluation Procedures for Degraded Buried Pipe. The Code Case addresses the nuclear industry need for evaluation procedures and acceptance criteria for the disposition of metal loss that is discovered during the inspection of metallic piping buried in a back-filled trench. A number of additional improvements have been proposed for Code Case N-806. These include expanded guidance for the determination and validation of a corrosion rate and other clarifications to improve ease of use. This paper presents an update of details of the proposed revisions to Code Case N-806 and their technical basis.

Author(s):  
Robert O. McGill ◽  
Mark A. Moenssens ◽  
George A. Antaki ◽  
Douglas A. Scarth

ASME Section XI Code Case N-806, for evaluation of metal loss in Class 2 and 3 metallic piping buried in a back-filled trench, was published in 2012. This Code Case has been prepared by the ASME Section XI Task Group on Evaluation Procedures for Degraded Buried Pipe. The Code Case addresses the nuclear industry need for evaluation procedures and acceptance criteria for the disposition of metal loss that is discovered during the inspection of metallic piping buried in a back-filled trench. A number of improvements have been proposed for Code Case N-806. These include improvements to the analytical procedures for structural integrity evaluation under soil and surcharge loads. In addition, tables of soil properties and other parameters needed in the evaluation are proposed to be provided to improve ease of use. This paper presents the technical basis for the proposed revision to Code Case N-806.


Author(s):  
Robert O. McGill ◽  
Mark A. Moenssens ◽  
George A. Antaki ◽  
Douglas A. Scarth

This paper presents the technical basis for Code Case N-806, Evaluation of Metal Loss in Class 2 and 3 Metallic Piping Buried in a Back-filled Trench – Section XI, Division 1. This Code Case has been prepared in the ASME Section XI Task Group on Evaluation Procedures for Degraded Buried Pipe. It addresses the nuclear industry need for evaluation procedures and acceptance criteria for the disposition of metal loss that may be discovered during the inspection of piping buried in a back-filled trench. This paper provides background discussion, scope of the Code Case, key definitions and a summary of Code Case methods followed by the basis explanation where necessary. It is organized to follow the same structure as the Code Case for ease of use.


Author(s):  
Robert O. McGill ◽  
George A. Antaki ◽  
Mark A. Moenssens ◽  
Douglas A. Scarth

Abstract ASME Section XI Code Case N-806, for evaluation of metal loss in Class 2 and 3 metallic piping buried in a backfilled trench, was first published in 2012. This Code Case has been prepared by the ASME Section XI Task Group on Evaluation Procedures for Degraded Buried Pipe. The Code Case addresses the nuclear industry need for evaluation procedures and acceptance criteria for the disposition of metal loss that is discovered during the inspection of metallic piping buried in a back-filled trench. In a second revision of the Code Case, several changes are proposed. First, guidance is provided for analytical evaluation of greater detail including finite element analysis methods. A new nonmandatory appendix is included to provide procedures for the evaluation of soil and surcharge loads using finite element analysis. Next, a second new nonmandatory appendix is provided giving detailed guidance on the evaluation of seismic loads. Finally, the need to evaluate the fatigue life of buried piping subjected to cyclic surface loading is now included and a design factor applied to the modulus of soil reaction is introduced. This paper presents details of the proposed changes to Code Case N-806-1 and their technical basis where applicable.


Author(s):  
Douglas A. Scarth ◽  
Michael Davis ◽  
Phil Rush ◽  
Steven X. Xu

Code Case N-597-2 provides procedures and acceptance criteria for the evaluation of piping items subjected to wall thinning mechanisms such as flow-accelerated corrosion (FAC). The acceptance criteria ensure that margins equivalent to those of the ASME B&PV Code are maintained. Subsequent to the publication of Code Case N-597-2, the U.S. Nuclear Regulatory Commission (NRC) found the Code Case conditionally acceptable. A number of task items have been undertaken by the ASME Section XI Working Group on Pipe Flaw Evaluation (WGPFE) to address the NRC conditions. A 2006 ASME Pressure Vessels and Piping (PVP) Division conference paper was published to provide an expanded explanation of the technical basis for Code Case N-597-2. A 2009 PVP paper was published to provide results of validation of evaluation procedures and acceptance criteria in Code Case N-597-2 against experimental and historic wall thinning events. More recently, revisions to Code Case N-597-2 have been made and were proposed as N-597-3. Significant changes have been made in the proposed revised Code Case to clarify the technical requirements and address the NRC concerns over N-597-2. The technical basis for revising Code Case N-597-2 is provided in this paper.


Author(s):  
Yong-Yi Wang ◽  
Ming Liu ◽  
David Horsley ◽  
Gery Bauman

Alternative girth weld defect acceptance criteria implemented in major international codes and standards vary significantly. The requirements for welding procedure qualification and the allowable defect size are often very different among the codes and standards. The assessment procedures in some of the codes and standards are more adaptive to modern micro-alloyed TMCP steels, while others are much less so as they are empirical correlations of test data available at the time of the standards creation. A major effort funded jointly by the US Department of Transportation and PRCI has produced a comprehensive update to the girth weld defect acceptance criteria. The newly proposed procedures have two options. Option 1 is given in an easy-to-use graphical format. The determination of allowable flaw size is extremely simple. Option 2 provides more flexibility and generally allows larger flaws than Option 1, at the expense of more complex computations. Option 1 also has higher fracture toughness requirements than Option 2, as it is built on the concept of plastic collapse. In comparison to some existing codes and standards, the new procedures (1) provide more consistent level of conservatism, (2) include both plastic collapse and fracture criteria, and (3) give necessary considerations to the most frequently occurring defects in modern pipeline constructions. This paper provides an overview of the technical basis of the new procedures and validation against experimental test data.


Author(s):  
Kunio Hasegawa ◽  
Yinsheng Li ◽  
Bostjan Bezensek ◽  
Phuong H. Hoang ◽  
Howard J. Rathbun

Piping components in power plants may experience combined bending and torsion moments during operation. There is a lack of guidance for pipe evaluation for pipes with local wall thinning flaws under the combined bending and torsion moments. ASME B&PV Code Section XI Working Group is currently developing fully plastic bending pipe evaluation procedures for pressurized piping components containing local wall thinning subjected to combined torsion and bending moments. Using elastic fully plastic finite element analyses, plastic collapse bending moments under torsions were obtained for 4 (114.3) to 24 (609.6) inch (mm) diameter pipes with various local wall thinning flaw sizes. The objective of this paper is to introduce an equivalent moment, which combines torsion and bending moments by a vector summation, and to establish the applicable range of wall thinning lengths, angles and depths, where the equivalent moments are equal to pure bending moments.


Author(s):  
Muntazir Abbas ◽  
Mahmood Shafiee ◽  
Nigel Simms

Abstract The composition of seawater plays a very significant role in determining the severity of corrosion process in marine assets. The influential contributors to the general and pitting corrosions in marine structures include temperature, dissolved oxygen (DO), salinity, PH, chlorides, pollutants, nutrients, and microbiological activities in seawater. The Cu-Ni (90/10) alloy is increasingly used in marine applications such as heat exchangers and marine pipelines because of its excellent corrosion resistant properties. Despite the significant advancements in corrosion shielding procedures, complete stoppage of corrosion induced metal loss, especially under rugged marine environments, is practically impossible. The selection of appropriate metal thickness is merely a multifaceted decision because of the high variability in operating conditions and associated corrosion rate in various seawater bodies across the globe. The present research study aims to analyze the early phase of corrosion behavior of Cu-Ni (90/10) alloy in open-sea conditions as well as in pollutant-rich coastal waters of the Arabian Sea. Test samples were placed under natural climatic conditions of selected sites, followed by the mass loss and corrosion rate evaluation. The corrosion rate in the pollutant-rich coastal waters was around five times higher than in the natural seawater. A case study on marine condenser (fitted with of Cu-Ni 90/10 alloy tubes) is presented, and a risk-based inspection (RBI) plan is developed to facilitate equipment designers, operators, and maintainers to consider the implications of warm and polluted seawater on equipment reliability, service life, and subsequent health inspection/ maintenance.


2018 ◽  
Vol 195 ◽  
pp. 04002
Author(s):  
Bagus Hario Setiadji

To date, non-destruction testing (NDT) method is the most popular method to assess the condition of road pavement. Among all evaluation procedures of the NDT method, load-deflection backcalculation analysis is one that is developed widely to understand the structural behavior of road pavement. On one side, the use of this analysis is greatly beneficial for presenting the layer characteristic accurately. However, the analysis requires specialist expertise. To overcome this, deflection bowl parameter application could become one alternative. The parameters are very easy to use; however, the intention of the parameters so far is only as an indication of the condition of the structural layer of the road pavement. Therefore, the parameters have to be used with careful consideration. In this study, the parameters were evaluated to determine the optimal usage of the parameters against different structures of road pavements. The results showed that a simplification of the number of parameters and a reformulation of the parameters were required by taking into account the ease of use in practice, the accuracy of subgrade modulus determination and the possibility to evaluate pavement structures with a layer number less than four.


Author(s):  
Terry Dickson ◽  
Shengjun Yin ◽  
Mark Kirk ◽  
Hsuing-Wei Chou

As a result of a multi-year, multi-disciplinary effort on the part of the United States Nuclear Regulatory Commission (USNRC), its contractors, and the nuclear industry, a technical basis has been established to support a risk-informed revision to pressurized thermal shock (PTS) regulations originally promulgated in the mid-1980s. The revised regulations provide alternative (optional) reference-temperature (RT)-based screening criteria, which is codified in 10 CFR 50.61(a). How the revised screening criteria were determined from the results of the probabilistic fracture mechanics (PFM) analyses will be discussed in this paper.


Author(s):  
Warren Bamford ◽  
Guy De Boo

Acceptance criteria have been developed for indications found during inspection of reactor vessel in upper head penetrations. These criteria were originally developed for inside surface flaws, as part of an industry program coordinated by NUMARC (now NEI) in 1992. These criteria were not inserted into Section XI at the time, because inspections were not required for these regions. In developing the enclosed acceptance criteria, the approach used by the industry group was similar to that used in other portions of Section XI, in that an industry consensus was reached using input from the operating utility technical staff, each of the three PWR vendors, and representatives of the NRC staff. The criteria developed are applicable to all PWR plant designs. The discovery of leaks at Oconee, ANO-1, and several other plants, have led to the imposition of inspection requirements for head penetration regions, and therefore the need to develop criteria for indications in all portions of the tubes. This would include indications on the inside diameter of the tube, as well as on the outside diameter of the tube below the attachment weld, and flaws in the attachment weld itself. The criteria presented herein are limits on flaw sizes which are acceptable. The criteria are to be applied to inspection results. It should be noted that determination of the period of future service during which the criteria are satisfied is plant-specific and dependent on flaw geometry and loading conditions. It has been previously demonstrated by each of the owners groups that the penetrations are very tolerant of flaws. It was concluded that complete fracture of the penetration would not occur unless very large through-wall flaws were present; therefore, protection against leakage during service is the priority. The approach used here is more conservative than that used in Section XI applications where the acceptable flaw size is calculated by putting a margin on the critical flaw size. In this case, the critical flaw size is far too large to allow a practical application of this approach, so protection against leakage is the key element used to define the acceptance criteria. Also, the use of flaw acceptance standards tables is not allowed for this region, for penetrations which are susceptible to stress corrosion cracking. The acceptance criteria apply to all flaw types regardless of orientation and shape. The same approach is used by Section XI, where flaws are characterized according to established rules and their future predicted size is then compared with the acceptance criteria.


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